Molecular Shape with Multiple Lone Pairs

(Polar molecules, Non-polar molecules, etc.)

Alex Nguyen 3I
Posts: 100
Joined: Fri Sep 25, 2015 3:00 am

Molecular Shape with Multiple Lone Pairs

Can anyone explain why the shape of a $I_{3}^{-}$ ion is linear? Does it have anything to do with the opposing repulsion of the lone pairs? I believe there are 3 on the central Iodine atom.

Nicholas Wu 3E
Posts: 23
Joined: Fri Sep 25, 2015 3:00 am

Re: Molecular Shape with Multiple Lone Pairs

I3- has a central iodine atom with two iodines singly bonded to it, and then 3 lone pairs. The AX2E3 arrangement is trigonal bipyramidal, with the three lone pairs arranged in a trigonal planar shape around them, with the iodines at opposite ends. Because shape does not take lone pairs into account, the molecular shape is linear.

Sparks55 3F
Posts: 18
Joined: Fri Sep 25, 2015 3:00 am

Re: Molecular Shape with Multiple Lone Pairs

Here is a picture that I hope will make what Alex Nguyen was saying more clear! If you just look at the atom-to-atom bond angles, they are all 180 degrees. The plane in which the lone pairs lie do not influence the bond angles in this case because they are symmetrically placed. Therefore we can conclude that the shape is linear :)
Attachments